This invention relates to a method and apparatus for shaping the distal surface of a human femur employing a novel adjustable shaping guide which is fixed to an intramedullary alignment guide which aligns with the central long axis of the femur.
In replacing a knee joint which has been damaged due to disease or trauma, it is very important that the prosthesis used to replace the damaged portion of the joint be properly aligned with respect to the bone to which the prosthesis is fixed. To enable a surgeon to shape the distal femur to receive a femoral component of a total knee joint prosthesis, Leo A. Whiteside, one of the named inventors herein, developed a method and apparatus for shaping a distal femoral surface which is claimed in U.S. Pat. No. 4,474,177 (issued 10/2/1984). That '177 Patent is hereby incorporated by reference to teach the use of an intramedullary alignment guide which provides the surgeon with a means for determining the central long axis of the femur and a means by which the surgeon can shape the distal femur relative to that axis by attaching distal femoral shaping instruments to that alignment guide. The '177 Patent teaches the use of a number of shaping guides to accomplish the shaping of the distal femoral surface. A more detailed surgical procedure describing this method of shaping the distal femur is described in Brochure No. L095-0201 9/85 entitled "Whiteside ORTHOLOC (.TM.) Total Knee System" from Dow Corning Wright Corporation, Arlington, TN (1985). Specific examples of two such shaping guide instruments described in that brochure (A/P Bevel Cutting Guide and Distal Cutting Guide) are shown in Brochure No. L095-PN003 entitled "New Whiteside ORTHOLOC (.TM.) Total Knee Instruments" also by Dow Corning Wright Corporation.
The shaping guide instruments described in the above patent and brochure lock onto the handle of the alignment guide and take their alignment from the position of the alignment guide handle. The surgeon selects the size of the prosthesis needed and a Standard, Large or Extra Large A/P Bevel Cutting Guide is fixed to the handle and the distal femoral surface is shaped using the guide surfaces on the Cutting Guide. The Distal Cutting Guide is adjustable to permit resection of the distal femoral condyles over a range of 6-10 millimeters. However, once the cutting guide is attached to the handle of the alignment guide, the guide surfaces on the cutting guide cannot be adjusted relative to the handle and thus relative to the surfaces of the femur being shaped. It is quite important that the anterior aspect of the distal femoral condyles be shaped relatively even with the anterior femoral cortical surface.
Brochure No. 86-038-5780-0525/16MA (1986) from Zimmer, Inc., Warsaw, Ind., entitled "ZIMMER (R) Intramedullary Knee Instrumentation For the Miller Galante Total Knee System" shows an Anterior Femoral Cutting Guide Instrument No. 5785-018 which uses a locator to reference the anterior femoral cortical surface and thus guide resection of the anterior aspects of the femoral condyles relative to that anterior cortical surface. That Guide Instrument is mounted on a Femoral IM (intramedullary) Alignment Guide No. 5785-012. However, the other distal femoral surfaces are then shaped after the IM Alignment Guide is removed from the femur and several different shaping guides are employed to accomplish the shaping of the femur.
Androphy, in U.S. Pat. No. 4,487,203 (issued 12/11/84), teaches a triplanar knee resection method which employs a single cutting guide member which is used in conjunction with L-shaped femur and tibia guide rods which are placed in the intramedullary canal to accomplish the shaping of the distal femur and the proximal tibia. The anterior and posterior aspects of the femoral condyles are shaped using the cutting guide member locked onto the L-shaped guide rod while the distal femoral condyles are shaped to a particular degree (based on a flexion gap determination) using a slidably adjustable bar which moves the cutting guide relative to the femoral guide rod.
Brochure No. 81-038-226-1020/15MZ entitled "Knee Replacement Using The INSALL/BURSTEIN Total Condylar Knee System" from Zimmer, Inc., Warsaw, IN (1981) teaches the use of a femoral hole locator which references the anterior femoral cortical surface to locate a point where a drill is used to provide an opening for a rod on which a separate femoral surface shaping guide is mounted. The shaping guide itself is not adjustable relative to the rod once the guide is mounted on the rod.
Lacey, in U.S. Pat. No. 4,502,483 (issued 3/5/1985), teaches a method and apparatus for shaping a distal femoral surface which uses an external alignment guide which has a main body which mounts on the surface of the anterior femoral cortex and employs femoral surface shaping guides whose shaping guide surfaces are adjusted relative to certain points on the distal femoral surface using locator pins. One such locator pin references the anterior surface intercondylar notch to align the shaping guide surfaces for shaping the anterior and posterior aspects of the distal femoral condyles. No intramedullary alignment guide is used with this apparatus.
Other examples of shaping guides which reference the anterior femoral cortical surface to accomplish the shaping of the posterior and anterior aspects of the distal femoral condyles can be found on pages 9-10 of Brochure No. 3246 Rev. 9-79 entitled "R.M.C. Total Knee System--Technique" from Richards Manufacturing Co., Inc., Memphis, TN (1979) and on page 14 and 20-12 of Brochure No. B-260-1 10M778 entitled "GEO-PATELLA (.TM.)/GEO-TIBIAL (.TM.) Total Knee --Surgical Technique" from Zimmer, Inc., Warsaw, IN (1977). Neither of these instruments employ intramedullary alignment guides to provide a reference point for the shaping guides.
In all of the above methods, multiple sets of shaping guides are generally employed to shape the distal femur.